In this kind of technical field, it is becoming more and more important to realize wideband radio access for performing high speed large capacity communication efficiently. Especially, as for downlink channels, a multicarrier scheme, more particularly, that is an Orthogonal Frequency Division Multiplexing (OFDM) scheme is considered promising from the viewpoint of performing high speed large capacity communications while suppressing multipath fading effectively, and the like. Then, performing frequency scheduling is also proposed in a next generation system in terms of improving throughput by increasing frequency use efficiency.
As shown in FIG. 1, a frequency band that can be used in the system is divided to a plurality of resource blocks (divided to three blocks in the example of the figure), and each of the resource blocks includes one or more subcarriers. The resource block is also called a frequency chunk. A terminal is assigned one or more resource blocks. In frequency scheduling, a resource block is assigned to a terminal in which channel state is good by priority according to received signal quality or channel state information (CQI: Channel Quality Indicator), of each of resource blocks of a downlink pilot channel, reported from terminals, so that transmission efficiency or throughput of the whole system is tried to improve. When frequency scheduling is performed, it is necessary to report content of the scheduling to the terminal, and the report is performed using a control channel (that may be called L1/L2 control signaling channel, associated control channel, low layer control channel, or the like). In addition, a modulation scheme (QPSK, 16 QAM, 64 QAM and the like, for example) used for the scheduled resource block, a channel coding information (channel coding rate and the like, for example), and a hybrid automatic retransmission request (HARQ: Hybrid Auto Repeat ReQuest) are transmitted using the control channel. The technique for dividing a frequency band into a plurality of resource blocks and changing modulation schemes for each resource block is described in the non-patent document 1, for example.
[Non-Patent Document 1]
    P. Chow, J. Cioffi, J. Bingham, “A Practical Discrete Multitone Transceiver Loading Algorithm for Data Transmission over Spectrally Shaped Channel”, IEEE Trans. Commun. vol. 43, No. 2/3/4, February/March/April 1995